The overall aim of this study is to examine whether estrogen will protect remitted depressed menopausal women from the transient relapse of depression after acute TRP depletion. Previous research has suggested that: 1) Peripheral and central measures of 5-HT activity are altered in depression: 2) SSRIs are effective in the treatment of depression: 3) estrogen has neuroregulatory activity on 5-HT function: 4) estrogen improves depressed mood.